kstat_queue(9F) Kernel Functions for Drivers kstat_queue(9F)NAME
kstat_queue, kstat_waitq_enter, kstat_waitq_exit, kstat_runq_enter,
kstat_runq_exit, kstat_waitq_to_runq, kstat_runq_back_to_waitq - update
I/O kstat statistics
SYNOPSIS
#include <sys/types.h>
#include <sys/kstat.h>
void kstat_waitq_enter(kstat_io_t *kiop);
void kstat_waitq_exit(kstat_io_t *kiop);
void kstat_runq_enter(kstat_io_t *kiop);
void kstat_runq_exit(kstat_io_t *kiop);
void kstat_waitq_to_runq(kstat_io_t *kiop);
void kstat_runq_back_to_waitq(kstat_io_t *kiop);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
kiop Pointer to a kstat_io(9S) structure.
DESCRIPTION
A large number of I/O subsystems have at least two basic "lists" (or
queues) of transactions they manage: one for transactions that have
been accepted for processing but for which processing has yet to begin,
and one for transactions which are actively being processed (but not
done). For this reason, two cumulative time statistics are kept: wait
(pre-service) time, and run (service) time.
The kstat_queue() family of functions manage these times based on the
transitions between the driver wait queue and run queue.
kstat_waitq_enter()kstat_waitq_enter() should be called when a request arrives and is
placed into a pre-service state (such as just prior to calling
disksort(9F)).
kstat_waitq_exit()kstat_waitq_exit() should be used when a request is removed from
its pre-service state. (such as just prior to calling the driver's
start routine).
kstat_runq_enter()kstat_runq_enter() is also called when a request is placed in its
service state (just prior to calling the driver's start routine,
but after kstat_waitq_exit()).
kstat_runq_exit()kstat_runq_exit() is used when a request is removed from its ser‐
vice state (just prior to calling biodone(9F)).
kstat_waitq_to_runq()kstat_waitq_to_runq() transitions a request from the wait queue to
the run queue. This is useful wherever the driver would have nor‐
mally done a kstat_waitq_exit() followed by a call to
kstat_runq_enter().
kstat_runq_back_to_waitq()kstat_runq_back_to_waitq() transitions a request from the run queue
back to the wait queue. This may be necessary in some cases (write
throttling is an example).
RETURN VALUES
None.
CONTEXTkstat_create() can be called from user or kernel context.
WARNINGS
These transitions must be protected by holding the kstat's ks_lock, and
must be completely accurate (all transitions are recorded). Forgetting
a transition may, for example, make an idle disk appear 100% busy.
SEE ALSObiodone(9F), disksort(9F), kstat_create(9F), kstat_delete(9F),
kstat_named_init(9F), kstat(9S), kstat_io(9S)
Writing Device Drivers
SunOS 5.10 4 Apr 1994 kstat_queue(9F)